There's no evidence that Twitter itself has been hacked. Instead, it seems that the stolen passwords, emails, and usernames were collected using malware that tricked people into entering their login information.

The release of the data is likely to cause another wave of Twitter account hacks and takeovers. We've already seen several high-profile accounts like the NFL, Katy Perry, Mark Zuckerberg, and Drake taken over because they likely reused their passwords. If one account is affected by a breach, then hackers are able to use that password to get into other accounts.